Injection molded container made of plastic

ABSTRACT

An injection molded cup-shaped container, made of plastic with a bottom and a container wall, which have a uniform thickness, from which bead-like thickenings protrude inward or outward. The thickenings start at a gate location in the bottom, have a radial course on the bottom, and extend on the container wall at a slant to the top edge of the container. The bead-like thickenings on the container wall and on the bottom are designed in such a way that the thickenings do not cross and each have a radius of curvature having a constant sign.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C.§371 of International Application No. PCT/EP2013/057543, filed on Apr.11, 2013, and claims benefit to German Patent Application No. DE 10 2012103 082.0, filed on Apr. 11, 2012. The International Application waspublished in German on Oct. 17, 2013, as WO 2013/153142 A1 under PCTArticle 21(2).

FIELD

The invention relates to an injection-molded plastic container.

BACKGROUND

Such a container is known from DE 72 27 210 U. Said container is a potproduced by injection molding. To keep material costs for the pot to aminimum, contours are formed in the pot wall which keep the pot wall,which should have as low a thickness as possible, sufficiently rigid.Various configurations are provided for the contours, such as linesextending straight towards the top edge of the pot, honeycombs, helices,optionally with crossing points.

Thin-walled pots are known which are produced by the thermoformingmethod, also known as extrusion or deep-drawing method, in whichgranular material is processed to form films from which the packagingparts are then drawn. This method is limited in terms of accuracy ofshape and wall distribution, and is restricted in terms of possiblegeometries and functions such as stacking of the products.

Another type of particularly thin-walled containers is produced by meansof injection molding methods. Generally, in this injection moldingmethod a plastic granular material is liquefied and injected into acavity at high pressure in the shortest possible time. The plasticmaterial is cooled in the cavity. The cooling re-hardens the liquidplastic material. When the mold is opened, the finished packaging can beremoved or ejected.

One advantage of the injection molding method is relatively highaccuracy along with a large degree of freedom in terms of shape. A largenumber of different geometries can be produced. The only requirement isthe demoldability of the parts, i.e. ensuring that it is possible toremove the produced part from the mold.

Following production of the product, pots and other plastic containersare conventionally printed on, labelled and/or sleeved, in other wordsenveloped with a heat shrink.

Nowadays, pots produced by means of injection molding are no longernormally decorated afterwards. Instead, pre-printed films are insertedinto the injection mold. This makes it possible to produce a finishedproduct in one operation. This approach is referred to as the in-moldlabelling method (IML). Attempts are currently being made to also usethe IML method in thermoforming methods. With the current state ofdevelopment, however, this causes significant loss of speed in thethermoforming method, since the packaging that has already been moldedfirst has to be demolded before films can be inserted. With injectionmolding, on the other hand, the film is inserted into the mold on oneside and the completely molded and decorated part is removed preferablyparallel on the other side, which may be the tool side.

One drawback of the IML method is that the available cross section ofthe cavity is disadvantageously reduced by the insert. The wall-flowratio, in other words the ratio of the longest flow path to the averagewall cross section, gets worse. As a result, premature hardening of themelt can occur sooner, and this increases the risk of the mold not beingcompletely filled. To compensate for this effect and to obtainform-fitting containers, it is necessary in line with the current stateof the art to select a relatively thick wall thickness. This leads toincreased material use and heavier pots, the result being higher costsfor material and for transport of the produced pots.

DE 26 14213 A1 discloses a method for improving filling. This methodaims to prevent premature hardening by means of pulsating pressurechanges. In this case, however, relatively large wall thicknesses wouldbe necessary when using the IML method. The wall thicknesses of the potsthus produced would not be optimal.

Pots are known which have various different flow promoters orientated inthe flow direction. As a result, the melt flow is facilitated in theflow direction by means of flow promoters. This leads to improvedfilling, and therefore relatively thin-walled pots can be produced. Theflow promoters form ridge-like thickenings leading vertically upwards inthe pot. One drawback of these pots, however, is that the flow promoterscause the plastic material to advance at a significantly higher speedduring production, and this leads to non-uniform filling of the regionsto be filled last. The wall thickness of the pot becomes less uniform.

The non-uniform filling, in an IML method, of the regions to be filledlast also means that the plastic material flows behind or in front ofthe insert. This leads to uncontrolled covering of the insert, which isknown as back-injection. The advance leads to visual degradation of theoverall impression of the pot. In addition, when the wall thickness isreduced, there is the risk of air being entrapped owing to the higheradvance speeds in the flow promoters, and this entrapment of air canlead to a lack of a form fit.

DE 20 46 958 describes a pot which attempts to solve the problem ofnon-uniform filling, in that the flow promoters, referred to as ribs,form an intersecting lattice. By defining the rib thicknesses to becloser relative to the wall thickness elsewhere, a container is producedwhich has uniform filling of the wall surfaces with a likewise uniformrib thickness.

SUMMARY

An aspect of the invention provides an injection-molded plasticcontainer, comprising: a bottom; a container wall; and an insert elementwhich is rigidly connected to the container in a label region on anoutside of the container wall. The container is produced by in-moldlabelling process. The bottom and the container wall have a uniformthickness. Ridge-like thickenings protrude inwards or outwards from thebottom and the container wall. The ridge-like thickenings start from agate mark in the bottom, have a radial course on the bottom, and extendon the container wall obliquely towards a top edge of the container. Theridge-like thickenings do not cross on the container wall and on thebottom. The ridge-like thickenings are formed as flow promotersconfigured to provide a uniform flow front of the plastic materialduring the in-mold labeling process.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in even greater detail belowbased on the exemplary figures. The invention is not limited to theexemplary embodiments. All features described and/or illustrated hereincan be used alone or combined in different combinations in embodimentsof the invention. The features and advantages of various embodiments ofthe present invention will become apparent by reading the followingdetailed description with reference to the attached drawings whichillustrate the following:

FIG. 1 a to FIG. 1 d are schematic views of the production of anembodiment of a container according to the invention during theproduction method.

DETAILED DESCRIPTION

The rib structure of the pot in this invention is preferably a rhomboid.If the rhombi are attached on the outside, in an IML method the labelsto be attached will also have a rhomboid structure. This leads torelatively poor legibility of the label and perception of the contents,depicted thereon, of the container. If the ribs are attached on theinside, removal from the molds is practically impossible. A rhomboidshape on the inside of pots is not desirable either. Smooth inner sidesallow the contents that have been filled in to be completely removed.The rhomboid shape, however, impairs removal, since the contents canonly be removed with difficulty from the rhombi between the intersectingribs, and can probably not be removed completely. There is the risk thatthe contents cannot be completely removed.

An aspect of the invention provides a container that is thin-walled andsturdy and can be produced in a mechanical production process in asimple and cost-effective manner.

An aspect of the invention provides an injection-molded plasticcontainer comprising a bottom and a container wall, the container walland the bottom each having a uniform thickness, from which ridge-likethickenings protrude inwards or outwards, which thickenings start from agate mark in the bottom, have a radial course on the bottom and extendobliquely on the container wall towards the top edge of the container.

An aspect of the invention provides a container, in which the ridge-likethickenings are formed such that they do not cross on the container walland on the bottom, and each comprise a radius of curvature of constantsign. The course of said thickenings is thus as diagonals or lines bentin one direction. This allows the containers to be produced having avery thin container wall by means of an injection molding method. Theridge-like thickenings are produced along flow promoters which areprovided in the injection mold and provided according to the shape ofthe ridge-like thickenings. Owing to the shape, according to theinvention, of the flow promoters, a uniform flow front of the plasticmaterial is ensured during the production process. As a result,entrapped air owing to premature hardening of the plastic material isprevented.

This course of the ridge-like thickenings deflects the melt flow suchthat, in the regions at risk of premature hardening or freezing, themelt flow is protected against premature hardening owing tocross-sectional reinforcement and maintenance of the fluid centre. Thiscauses the melt front to flow almost uniformly into all regions to befilled. Uniform filling is thereby ensured. At the same time, moltenplastic material is also prevented from advancing too quickly into theregions of the flow promoters and running back down. This savesunnecessary material on the one hand and, in an IML method, alsoprevents the insert element from being partly covered by drippingplastic material in the regions in which an insert element has beenapplied, or prevents the insert element from being back-injected owingto the faster advance of the liquid plastic material, since the plasticmaterial flows behind the insert element in an uncontrolled manner.

Owing to the course, according to an aspect of the invention, of theridge-like thickenings of the pot, simple demolding of the pot is alsoensured. Since the ridge-like thickenings are only curved in onedirection, the pot can be removed from the mold simply, by a rotationmovement, and without the risk of damage. This means that the method canbe carried out in a completely automatic manner to the end, andtherefore the method is simplified and costs can be reduced. Completeremoval of a material with which the container is filled during use isalso facilitated by the shape, according to the invention, of theridge-like thickenings.

According to an advantageous development of the invention, theinclination of the ridge-like thickenings on the container wall isselected such that the angle of inclination N relative to the bottom isfor example between 30° and 60°. This allows particularly good resultsto be achieved in terms of a flow front of the plastic melt with aconstant speed, so that the container has the desired thin, smooth,resilient and sturdy side wall. It can also be advantageous if theradius of curvature of the ridge-like thickenings increases towards thetop edge of the container. As a result, the vertical and thus leadingcomponents of the liquid plastic material can be reduced further towardsthe end of the process, it being possible thereby to achieve an evenmore uniform and thinner container wall of the container. It isadvantageous if the ridge-like thickenings have a constant and at leastpartly round cross section. The cross section can be half-round, roundor even oval. This ensures high stability and simple removal from themold.

According to an advantageous development of the invention, branchesstarting from the ridge-like thickenings are provided, the length andcross section of which branches are smaller than the length and crosssection of the ridge-like thickenings, the branches not crossing oneanother or the thickenings.

The size and orientation of the ridge-like thickenings produced by theflow promoters are tailored to the desired product and requirements andis determined according to the most favorable wall-flow ratio and thematerial used for the specific container to be produced. To ensureuniform wall thickness even in products having a relatively largesurface area, it is additionally expedient in individual cases to branchthe ridge-like thickenings in a similar manner to the vascular system ofthe human body or to provide smaller branches or branches of the samesize that branch from the respective main arm of the respective flowpromoter at any given angle according to requirements and size of theproduct to be injection-molded. As a result, the container then has ablood-vessel-like system of thickenings, either on the inner wall or theouter wall of the container as desired. The uniform distribution, madepossible thereby, of the plastic material over the entire region of thecontainer ensures that the entire wall of the container is filled withplastic material. At the same time, back-injection of potential insertelements is prevented.

Advantageously, a thickening is provided on the top edge of thecontainer and is formed cohesively with the container wall. This ensuresa sturdy region of the container, to which region a lid can be applied.

According to an advantageous embodiment of the invention, the containerwall comprises a first region in which the ridge-like thickenings have agreater cross section than in the second region, whereby the containerwall has a greater height in the first region than in the second region.According to another advantageous embodiment of the invention, thecontainer wall comprises a first region in which the ridge-likethickenings are closer together than in a second region, whereby thecontainer wall has a greater height in the first region than in thesecond region. Owing to the arrangement and configuration, used in thiscase, of the flow promoters, accelerated flow and later hardening of themelt front is brought about in the first region of the container wallduring the production process. As a result, more plastic material isfilled into these regions. The ability of the melt front to flow for alonger period of time allows for a longer pot wall. A container isproduced that has different length walls yet is filled completely. Theridge-like thickenings on the longer container surfaces are designed tobe thicker, and those on the shorter container surfaces arecorrespondingly thinner. This ensures that, apart from the ridge-likethickenings, the wall thickness is as uniform and as thin as possible.

According to an advantageous embodiment of the invention, an insertelement, in particular a paper strip, a plastic strip or a film, ispermanently connected to the container in a label region on the outerside of the container wall as a result of the injection molding method.The container has been produced by means of an IML method, in which theinsert element is inserted into the injection mold before the moltenplastic material in injected into the injection mold. In this regard,the uniform course of the melt front as a result of the arrangement,according to the invention, of the flow promoters and the ridge-likethickenings is particularly advantageous, since the insert elements areconnected to the container in a simple manner in the production process,without said elements being covered by plastic material or havingplastic material run behind them. Completely legible labels can thus beapplied to the container in a permanent, smooth, reliable and simplemanner.

Advantageously, containers can be formed having different edge lengthsof the insert element, since it is possible, owing to different designsof the flow promoters, to provide the flow front to all ends of theinsert at the same time within the mold. This allows for containershaving correspondingly variable insert elements while being filledcompletely.

According to the invention, the container can also comprise a differentmaterial than plastic material, provided that the material is suitablefor processing in an injection molding method. The exact course of theflow promoters, along with their shape, cross section, density, number,and shape and number of the branches, can be optimized according to theinvention in that these and similar dimensions can be optimizedmathematically for specific product requirements, such as the size ofthe container, the desired or required wall thickness, the desiredthickness and shape of the upper container end or the thickening on thetop edge of the container, etc.

FIG. 1 a to 1 d show the production of a container 1. The shapingrelevant for the container 1 is shown schematically by an injectionmold. The cavity of the injection mold is designed to shape thecontainer 1 to have a bottom 2 and a container wall 3. Ridge-likethickenings 4 are provided on the bottom 2 and on the container wall 3in regions provided therefor and protrude out from the bottom 2 and thecontainer wall 3. In the intermediate regions between the ridge-likethickenings 4, the bottom 2 and the container wall 3 of the container 1to be produced have a uniform thickness. On the bottom 2, the ridge-likethickenings 4 are formed radially. In the embodiment shown, saidthickenings extend in point symmetry with respect to the center M of thebottom 2 and are slightly curved, the sign of the radius of curvaturenot changing. The ridge-like thickenings 4 on the container wall 3extend obliquely from the bottom 2 towards the top edge 5 of thecontainer 1 and are bent in one direction, said thickenings having aradius of curvature, the sign of which does not change. A thickening isprovided on the top edge 5 of the container 1, to which thickening a lidcan be applied. The ridge-like thickenings 4 have a constant and roundcross section. In the embodiment shown, the arrangement is selected tobe axisymmetrical to the perpendicular through the center M of thebottom 2, so as to produce a symmetrical container 1.

FIG. 1 a shows a first step of the injection molding method forproducing the container 1. Liquefied plastic material or anothermaterial suitable for this method is injected into the cavity of theinjection mold at a gate mark located at the center M of the bottom 2,and spreads out axisymmetrically to the perpendicular through the centerM. In the process, the ridge-like thickenings 4 form flow promoters.Owing to the shape and arrangement of the flow promoters, the flow frontof the liquid plastic material spreads out uniformly and at a constantflow speed until the bottom 2 is uniformly covered, as shown in FIG. 1b. Owing to the uniform melt flow of the plastic material, the bottom 2of the pot 1 has a uniform thickness in the regions between thethickenings 4. As shown in FIG. 1 c, the liquid plastic material risesupwards, uniformly and at a constant speed, along the flow front bymeans of the flow promoters on the container wall 3 as far as up to thetop edge 5, the container 1 shown in FIG. 1 d being produced. In theprocess, the thickening on the top edge 5 is filled with plasticmaterial. The container wall 3 has a constant uniform thickness in theregions between the ridge-like thickenings 4. The ridge-like thickenings4 are selected depending on the product requirements. They can also beformed such that the bottom has a different thickness than the containerwall.

In the cavity of the injection mold, an insert element can be insertedin the region of the container wall, which element is rigidly connectedto the plastic material and thus to the container wall 3 duringproduction. Owing to the uniform flow of the plastic material, theinsert element adheres rigidly to the surface of the container wall 3and is not covered with plastic material.

The problem is solved by the present invention by means of specificshaping and orientation of the flow promoters (also termed supplyridges) which are designed as ribs or ridge-like thickenings in thecontainer. During the production process, the faster advance, whichbegins, of the plastic material is guided over the surfaces to be filledvia an optimum course of the flow promoters, so that ridge-like shapesin the form of the flow promoters are produced in a mirror image. Theridge-like shapes are not orientated, or not exclusively orientated, inthe flow direction, but rather, according to requirements, are guidedaround the mold of the container to be produced, in a curved shape or indiagonal positions or, depending on the size and the need to maintainthe flowability, in oblique positions relative to the flow direction.

The supply ridges are introduced in the device, in particular in theinjection molding tools. Here, it is unimportant in terms of thecontainer and the production thereof whether said ridges are attached onthe inside or on the outside. In this respect, the present inventiondiffers significantly from the solution described in DE 20 46 958 B2, inwhich, because of the need to ensure demoldability, it is compulsory forthe ribs to be positioned on the outside since shrinkage always has betaken into consideration during production. This shrinkage means thatthe rhombi effectively attach themselves to the mold. With rhombi on theinside, demolding is not possible without causing destruction.

By means of the optimum course of the ridge-like thickenings, whichcourse can be determined according to the product requirements, the meltflow is deflected from the actual flow direction during production, suchthat the flowable plastic material flows in a targeted manner, throughcross sections which have been adapted accordingly in terms of size,until it reaches the desired regions in which premature hardening wouldoccur without appropriate assistance. This technical solution means thatthe melt flows almost uniformly into all regions, even those to befilled last. Depending on the production requirements in terms of sizeand desired or required wall thickness and depending on the desiredthickness and shape of the upper end region of the pot, the ridge-likethickenings are laid out as paths, so that during production the plasticmaterial is deflected from the actual flow direction in the mannerrequired in each case. A container is produced that has correspondinglyoblique ridge-like thickenings and low wall thickness at the same time.With the exception of the ridge-like thickenings, which are due to thetechnical requirements within the scope of the production process, saidwall thickness is kept as low as possible by the targeted deflection ofthe plastic material from the flow direction.

A container that has a particularly thin wall is thus made possible. Theridge-like thickenings are located on the inside. The ridge-likethickenings do not cross; they are in an oblique position relative tothe pot wall. The pot can be demolded by a rotation movement counter tothe oblique direction of the ribs. If demolding is not possible or notcompletely possible by a rotation movement either owing to thearrangement of the ridge-like thickenings or the shape of the container,in the event of instantaneous demolding following production demoldingcan be carried out completely or in part by being rapidly slipped overthe device owing to the low wall thickness and the flexibility as aresult of the residual heat.

The invention is applicable in particular in the following areas: foodcontainers, in particular pots for holding foodstuffs which are liquidor viscous but which solidify after filling, provided the foodstuffs tobe filled into the containers are not corrosive to plastic materials;other containers and pots or products, in particular for holding liquid,viscous or such substances that are not corrosive to plastic materialand that solidify after being filled in a liquid or viscous state, orcontainers for holding solid substances or products.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive. Itwill be understood that changes and modifications may be made by thoseof ordinary skill within the scope of the following claims. Inparticular, the present invention covers further embodiments with anycombination of features from different embodiments described above andbelow. Additionally, statements made herein characterizing the inventionrefer to an embodiment of the invention and not necessarily allembodiments.

The terms used in the claims should be construed to have the broadestreasonable interpretation consistent with the foregoing description. Forexample, the use of the article “a” or “the” in introducing an elementshould not be interpreted as being exclusive of a plurality of elements.Likewise, the recitation of “or” should be interpreted as beinginclusive, such that the recitation of “A or B” is not exclusive of “Aand B,” unless it is clear from the context or the foregoing descriptionthat only one of A and B is intended. Further, the recitation of “atleast one of A, B, and C” should be interpreted as one or more of agroup of elements consisting of A, B, and C, and should not beinterpreted as requiring at least one of each of the listed elements A,B, and C, regardless of whether A, B, and C are related as categories orotherwise. Moreover, the recitation of “A, B, and/or C” or “at least oneof A, B, or C” should be interpreted as including any singular entityfrom the listed elements, e.g., A, any subset from the listed elements,e.g., A and B, or the entire list of elements A, B, and C.

1. An injection-molded plastic container, comprising: a bottom; acontainer wall; and an insert element which is rigidly connected to thecontainer in a label region on an outside of the container wall, whereinthe container is produced by in-mold labelling process, wherein thebottom and the container wall have a uniform thickness, whereinridge-like thickenings protrude inwards or outwards from the bottom andthe container wall, wherein the ridge-like thickenings start from a gatemark in the bottom, have a radial course on the bottom, and extend onthe container wall obliquely towards a top edge of the container,wherein the ridge-like thickenings do not cross on the container walland on the bottom, and wherein the ridge-like thickenings are formed asflow promoters configured to provide a uniform flow front of the plasticmaterial during the in-mold labelling process.
 2. The container of claim1, wherein the ridge-like thickenings are formed such that during thein-mold labelling process the uniform flow front of liquid plasticmaterial spreads out on the bottom and on the container wall at aconstant speed in each case.
 3. The container of claim 1, wherein acourse and a cross-section of the ridge-like thickenings are optimizedfor specific product requirements.
 4. The container of claim 1, whereinthe ridge-like thickenings have a constant and at least partly roundcross section.
 5. The container of claim 1, further comprising: branchesstarting from the ridge-like thickenings, wherein a length and crosssection of the branches are smaller than a length and cross section ofthe ridge-like thickenings, wherein the branches do not cross oneanother or the ridge-like thickenings.
 6. The container of claim 1,further comprising: a top edge thickening on the top edge of thecontainer, wherein the top edge thickening is formed cohesively with thecontainer wall.
 7. The container of claim 1, wherein the container wallincludes a first region and a second region, wherein, in the firstregion, the ridge-like thickenings have a greater cross section than inthe second region, and wherein the container wall has a greater heightin the first region than in the second region.
 8. The container of claim1, wherein the container wall includes a first region and a secondregion, wherein, in the first region, the ridge-like thickenings arecloser together than in a second region, and wherein the container wallhas a greater height in the first region than in the second region. 9.The container of claim 1, further comprising: a label, wherein the labelhas different edge lengths, wherein, during production of the ridge-likethickenings, the label is shaped such that the uniform flow front of theplastic material is provided to all ends of the label at a same time.10. The container of claim 6, wherein the top edge thickening is formedintegrally with the container wall.
 11. The container of claim 1,wherein the container wall includes a first region and a second region,wherein, in the first region, the ridge-like thickenings have a greatercross section than in the second region.
 12. The container of claim 1,wherein the container wall includes a first region and a second region,wherein, in the first region, the ridge-like thickenings are closertogether than in a second region.
 13. The container of claim 1, whereinthe container wall includes a first region and a second region, whereinthe container wall has a greater height in the first region than in thesecond region.